One of the world’s biggest clothing buyers, the U.S. government, spends more than $1.5 billion a year at factories overseas, acquiring everything from the royal-blue shirts worn by airport security workers to the olive button-downs required for forest rangers and the camouflage pants sold to troops on military bases.

But even though the Obama administration has called on Western buyers to use their purchasing power to push for improved industry working conditions after several workplace disasters over the past 13 months, the U.S. government has done little to adjust its own shopping habits.

Labor Department officials say that federal agencies have a “zero tolerance” policy on using overseas plants that break local laws, but U.S. government suppliers in countries including Bangladesh, the Dominican Republic, Haiti, Mexico, Pakistan and Vietnam show a pattern of legal violations and harsh working conditions, according to audits and interviews at factories. Among them: padlocked fire exits, buildings at risk of collapse, falsified wage records and repeated hand punctures from sewing needles when workers were pushed to hurry.

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In Bangladesh, shirts with Marine Corps logos sold in military stores were made at DK Knitwear, where child laborers made up a third of the workforce, according to a 2010 audit that led some vendors to cut ties with the plant. Managers punched workers for missed production quotas, and the plant had no functioning fire-alarm system despite previous blazes, auditors said. Many of the problems remain, according to another audit this year and recent interviews with workers.

In Chiang Mai, Thailand, employees at the Georgie & Lou factory, which makes clothing sold by the Smithsonian Institution, said they were illegally docked more than 5 percent of their roughly $10-per-day wage for any clothing item with a mistake. They also described physical harassment by factory managers and cameras monitoring workers even in bathrooms.

At Zongtex Garment Manufacturing in Phnom Penh, Cambodia, which makes clothes sold by the Army and Air Force, an audit conducted this year found nearly two dozen underage workers, some as young as 15. Several of them described in interviews with The New York Times how they were instructed to hide from inspectors.

“Sometimes people soil themselves at their sewing machines,” one worker said, because of restrictions on bathroom breaks.

Federal agencies rarely know what factories make their clothes, much less require audits of them, according to interviews with procurement officials and industry experts. The agencies, they added, exert less oversight of foreign suppliers than many retailers do. And there is no law prohibiting the federal government from buying clothes produced overseas under unsafe or abusive conditions.

“It doesn’t exist for the exact same reason that American consumers still buy from sweatshops,” said Daniel Gordon, a former top federal procurement official who now works at George Washington University Law School. “The government cares most about getting the best price.”

Labor and State Department officials have encouraged retailers to participate in strengthening rules on factory conditions in Bangladesh — home to one of the largest and most dangerous garment industries. But defense officials this month helped kill a legislative measure that would have required military stores, which last year made more than $485 million in profit, to comply with such rules because they said the $500,000 annual cost was too expensive.

Federal spending on garments overseas does not reach that of Wal-Mart, the world’s biggest merchandiser, which spends more than $1 billion a year just in Bangladesh, or Zara, the Spanish apparel seller, but it still is in a top tier that includes H&M, the trendy fashion business based in Sweden, Eddie Bauer and Lands’ End, sellers of outerwear and other clothing.

Like most retail brands, U.S. agencies typically do not order clothes directly from factories. They rely on contractors. This makes it challenging for agencies to track their global supply chain, with layers of middlemen, lax oversight by other governments, few of their own inspectors overseas and little means of policing factories that farm out work to other plants without the clients’ knowledge. When retailers, labor groups or others inspect these factories, the audits often understate problems because managers regularly coach workers and change records.

The Obama administration has favored free-trade agreements to spur development in poor countries by cultivating low-skill, low-overhead jobs like those in the cut-and-sew industry.

Along a dirt road in Gazipur, about 25 miles north of the Bangladeshi capital, riot police fired tear-gas shells, rubber bullets and sound grenades in a fierce clash with garment workers last month, sending scores to the hospital. The protesters demanding better conditions included some from a factory called V&R Fashions. In July, auditors rated that factory as “needs improvement” because workers’ pay was illegally docked for minor infractions and the building was unsafe, illegally constructed and not intended for industrial use.

Like dozens of other factories in the area, V&R makes clothes for the U.S. government, which is constantly prowling for the best deals.

Conditions like those are possible partly because U.S. government agencies usually do not know which factories supply their goods or are reluctant to reveal them. Soon after a fire killed at least 112 people at the Tazreen Fashions factory in Bangladesh in November 2012, several members of Congress asked various agencies for factory addresses. Of the seven agencies her office contacted, Rep. Carolyn Maloney, D-N.Y., said only the Department of the Interior turned over its list.

Over the summer, military officials told Rep. George Miller, D-Calif., that order forms for apparel with Marine Corps logos had been discovered in Tazreen’s charred remains but that the corps had ties to no other Bangladeshi factories. Several weeks later, the officials said they were mistaken and had discovered a half-dozen or so other factories producing unauthorized Marine Corps apparel. On Sunday, the owners of Tazreen and 11 employees were charged with culpable homicide.

President Obama has long pushed for more transparency in procurement. As a senator, he sponsored legislation in 2006 creating the website USASpending.gov, which open-government advocates say has made it far easier to track federal contracting. However, procurement experts fault the website for requiring agencies to name their contractors, but not identifying the specific factories doing the work.

Defense officials, however, who spend roughly $2 billion annually on military uniforms, are required by a World War II-era rule called the Berry Amendment to have most of them made in the United States. In recent years, Congress has pressured defense officials to cut costs on uniforms. Increasingly, the department has turned to federal prisons, where wages are under $2 an hour. Federal inmates this year stitched more than $100 million worth of military uniforms.

No sooner had the Transportation Security Administration (TSA) signed a $50 million contract in February for new uniforms for its 50,000 airport security agents and other workers than the agency was attacked from all sides.

Union officials, opposed to outsourcing work overseas, objected because the Mexican plant making the clothing, VF Imagewear Matamoros, was the same one that had treated uniforms with chemicals that caused rashes in hundreds of TSA agents. Congress called an oversight hearing, where some lawmakers questioned why two-thirds of the uniforms would be made in foreign factories, saying the deal was a missed chance to stimulate domestic job growth.

In Haiti, for instance, trucks loaded with camouflage pants, shirts and jackets, some of them destined for U.S. military bases, idle in front of a factory called BKI.

Next year, BKI managers hope to double the amount of camouflage clothing made for the U.S. government, part of a contract worth more than $30 million between a division of Propper International, a Missouri-based uniform company, and the General Services Administration, which outfits workers for more than a dozen federal agencies.

Three years ago, much of this camouflage clothing was made in Puerto Rico, where workers earned the minimum wage of about $7.25 an hour. By 2011, many of these jobs moved to a factory in the Dominican Republic called Suprema. Wages there were about 80 cents per hour and unpaid overtime was routine, according to workers in recent interviews and a 2010 audit. Since then, most of these jobs have migrated again, this time to BKI in a Haitian free-trade zone called Codevi. Average hourly wages at BKI are about 8 cents less per hour than those at Suprema, according to workers.